US7582027B2 - Negative hardness gradient inner core for dual core golf ball - Google Patents

Negative hardness gradient inner core for dual core golf ball Download PDF

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US7582027B2
US7582027B2 US12/186,924 US18692408A US7582027B2 US 7582027 B2 US7582027 B2 US 7582027B2 US 18692408 A US18692408 A US 18692408A US 7582027 B2 US7582027 B2 US 7582027B2
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hardness
core
shore
bis
phr
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US20090011859A1 (en
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David A. Bulpett
Brian Comeau
Derek A. Ladd
Michael J. Sullivan
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Acushnet Co
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Acushnet Co
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Priority claimed from US11/772,903 external-priority patent/US7537529B2/en
Priority claimed from US11/829,461 external-priority patent/US7537530B2/en
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    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0077—Physical properties
    • A63B37/0092—Hardness distribution amongst different ball layers
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/0038—Intermediate layers, e.g. inner cover, outer core, mantle
    • A63B37/004—Physical properties
    • A63B37/0043—Hardness
    • A63B37/0044—Hardness gradient
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/0051—Materials other than polybutadienes; Constructional details
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0062—Hardness
    • A63B37/00621—Centre hardness
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0062—Hardness
    • A63B37/00622—Surface hardness
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0062—Hardness
    • A63B37/0063—Hardness gradient
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/005—Cores
    • A63B37/006—Physical properties
    • A63B37/0064—Diameter
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0072—Characteristics of the ball as a whole with a specified number of layers
    • A63B37/0075—Three piece balls, i.e. cover, intermediate layer and core
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0072—Characteristics of the ball as a whole with a specified number of layers
    • A63B37/0076—Multi-piece balls, i.e. having two or more intermediate layers
    • A—HUMAN NECESSITIES
    • A63—SPORTS; GAMES; AMUSEMENTS
    • A63B—APPARATUS FOR PHYSICAL TRAINING, GYMNASTICS, SWIMMING, CLIMBING, OR FENCING; BALL GAMES; TRAINING EQUIPMENT
    • A63B37/00—Solid balls; Rigid hollow balls; Marbles
    • A63B37/0003—Golf balls
    • A63B37/007—Characteristics of the ball as a whole
    • A63B37/0077—Physical properties
    • A63B37/008—Diameter

Definitions

  • This invention relates generally to golf balls with cores, more particularly single layer cores, having a surface hardness equal to or less than the center hardness.
  • Solid golf balls are typically made with a solid core encased by a cover, both of which can have multiple layers, such as a dual core having a solid center and an outer core layer, or a multi-layer cover having an inner.
  • golf ball cores and/or centers are constructed with a thermoset rubber, typically a polybutadiene-based composition.
  • the cores are usually heated and crosslinked to create certain characteristics, such as higher or lower compression, which can impact the spin rate of the ball and/or provide better “feel.” These and other characteristics can be tailored to the needs of golfers of different abilities. From the perspective of a golf ball manufacturer, it is desirable to have cores exhibiting a wide range of properties, such as resilience, durability, spin, and “feel,” because this enables the manufacturer to make and sell many different types of golf balls suited to differing levels of ability.
  • U.S. Pat. No. 4,650,193 to Molitor et al. generally discloses a hardness gradient in the surface layers of a core by surface treating a slug of curable elastomer with a cure-altering agent and subsequently molding the slug into a core.
  • This treatment allegedly creates a core with two zones of different compositions, the first part being the hard, resilient, central portion of the core, which was left untreated, and the second being the soft, deformable, outer layer of the core, which was treated by the cure-altering agent.
  • the two “layers” or regions of the core are integral with one another and, as a result, achieve the effect of a gradient of soft surface to hard center.
  • U.S. Pat. No. 3,784,209 to Berman, et al. generally discloses a soft-to-hard hardness gradient.
  • the '209 patent discloses a non-homogenous, molded golf ball with a core of “mixed” elastomers.
  • a center sphere of uncured elastomeric material is surrounded by a compatible but different uncured elastomer.
  • both layers of elastomer are concurrently exposed to a curing agent, they become integral with one another, thereby forming a mixed core.
  • the center of this core, having a higher concentration of the first elastomeric material is harder than the outer layer.
  • One drawback to this method of manufacture is the time-consuming process of creating first elastomer and then a second elastomer and then molding the two together.
  • each core layer has a different hardness thereby creating a hardness gradient from core layer to core layer.
  • the present invention is directed to a golf ball having an inner core having a first outer surface and a geometric center and being formed from a first substantially homogenous formulation throughout such that the inner core generally has a hardness in the range of 45 Shore C to 65 Shore C; an outer core layer disposed about the inner core having a second outer surface and an inner surface and being formed from a second substantially homogenous formulation throughout such that the outer core layer generally has a hardness in the range of 55 Shore C to 90 Shore C.
  • a cover layer is disposed about the outer core layer.
  • the hardness of the first outer surface is the same as or lower than the hardness of the geometric center to define a “negative hardness gradient” and the hardness of the second outer surface is greater than the hardness of the inner surface to define a “positive hardness gradient.”
  • the inner core includes a metal salt of a carboxylic acid in an amount of about 15 phr to about 30 phr and has a ratio of antioxidant to initiator of about 0.40 or greater, preferably 0.50 or greater, when normalized to 100% activity, and the outer core layer includes a metal salt of a carboxylic acid in an amount of about 30 phr to about 45 phr.
  • the initiator is typically present in the amount from about 0.25 phr to about 5.0 phr at 100% activity and the antioxidant is typically present in amount of about 0.2 phr to about 1 phr.
  • the hardness of the first outer surface is 42 Shore C to 60 Shore C
  • the hardness of the geometric center is 52 Shore C to 65 Shore C
  • the “negative hardness gradient” has a magnitude of about 0 to ⁇ 10.
  • the hardness of the second outer surface is 62 Shore C to 89 Shore C
  • the hardness of the inner surface is 58 Shore C to 82 Shore C
  • the “positive hardness gradient” has a magnitude of 10 to 20.
  • the inner core has an outer diameter of 0.75 inches to 1.4 inches and the outer core layer has an outer diameter of 1.5 inches to 1.59 inches.
  • the cover layer typically includes an inner cover layer and an outer cover layer.
  • the inner core and the outer core layer may be formed from a diene rubber composition and, optionally, include a soft and fast agent.
  • the present invention is also directed to a golf ball having an inner core having a first outer surface and a geometric center and being formed from a first substantially homogenous formulation throughout such that the inner core generally has a hardness in the range of 60 Shore C to 90 Shore C; an outer core layer having a second outer surface and an inner surface and being formed from a second substantially homogenous formulation throughout such that the outer core layer generally has a hardness in the range of 45 Shore C to 70 Shore C; and a cover layer.
  • the geometric center, the first and second outer surfaces, and the inner surface each have a hardness.
  • the hardness of the first outer surface is the same as or lower than the hardness of the geometric center to define a “negative hardness gradient” and the hardness of the second outer surface is greater than the hardness of the inner surface to define a “positive hardness gradient.”
  • the inner core includes a metal salt of a carboxylic acid in an amount of about 30 phr to about 45 phr and has a ratio of antioxidant to initiator of about 0.40 or greater, preferably about 0.50 or greater, when normalized to 100% activity
  • the outer core layer includes a metal salt of a carboxylic acid in an amount of about 15 phr to about 30 phr.
  • the initiator may be present in the amount from about 0.25 phr to about 5.0 phr at 100% activity and the antioxidant may be present in amount of about 0.2 phr to about 1 phr.
  • the hardness of the first outer surface is 61 Shore C to 83 Shore C
  • the hardness of the geometric center is 65 Shore C to 86 Shore C
  • the “negative hardness gradient” has a magnitude of about 0 to ⁇ 10.
  • the hardness of the second outer surface is 52 Shore C to 68 Shore C
  • the hardness of the inner surface is 49 Shore C to 63 Shore C
  • the “positive hardness gradient” has a magnitude of 10 to 20.
  • the inner core typically has an outer diameter of 0.75 inches to 1.4 inches and the outer core layer has an outer diameter of 1.5 inches to 1.59 inches.
  • the cover layer preferably includes an inner cover layer and an outer cover layer.
  • the inner core and the outer core layer may include a diene rubber composition and, optionally, include a soft and fast agent.
  • the present invention is further directed to a golf ball formed from an inner core having a first outer surface and a geometric center and is formed from a first substantially homogenous formulation throughout such that the inner core generally has a hardness in the range of 40 Shore C to 80 Shore C.
  • An outer core layer is formed around the inner core and has a second outer surface and an inner surface and formed from a second substantially homogenous formulation throughout such that the outer core layer generally has a hardness in the range of 60 Shore C to 90 Shore C.
  • a cover layer having at least two layers is formed around the outer core layer.
  • the hardness of the first outer surface is the same as or lower than the hardness of the geometric center to define a “negative hardness gradient” and the hardness of the second outer surface is greater than the hardness of the inner surface to define a “positive hardness gradient” such that the hardness of the inner surface and the first outer surface are the same and both less than the hardness at the geometric center and the second outer surface.
  • the inner core and the outer core layer typically include a diene rubber composition and, optionally, include a soft and fast agent.
  • FIG. 1 is a graph of the hardness of the core as a function of the distance from its center for both inventive cores and comparative example cores;
  • FIG. 2 is a graph depicting preferred hardness ranges for a “low spin” embodiment of the present invention.
  • FIG. 3 is a graph depicting preferred hardness ranges for a “high spin” embodiment, of the present invention.
  • the golf balls of the present invention may include a single-layer (one-piece) golf ball, and multi-layer golf balls, such as one having a core and a cover surrounding the core, but are preferably formed from a core comprised of a solid center (otherwise known as an inner core) and an outer core layer, an inner cover layer and an outer cover layer.
  • a core comprised of a solid center (otherwise known as an inner core) and an outer core layer, an inner cover layer and an outer cover layer.
  • any of the core and/or the cover layers may include more than one layer.
  • the core is formed of an inner core and an outer core layer where both the inner core and the outer core layer have a “soft-to-hard” hardness gradient (a “negative” hardness gradient) radially inward from each component's outer surface towards its innermost portion (i.e., the center of the inner core or the inner surface of the outer core layer), although alternative embodiments involving varying direction and combination of hardness gradient amongst core components are also envisioned (e.g., a “negative” gradient in the center coupled with a “positive” gradient in the outer core layer, or vice versa).
  • a “soft-to-hard” hardness gradient a “negative” hardness gradient
  • the center of the core may also be a liquid-filled or hollow sphere surrounded by one or more intermediate and/or cover layers, or it may include a solid or liquid center around which tensioned elastomeric material is wound. Any layers disposed around these alternative centers may exhibit the inventive core hardness gradient (i.e., “negative”).
  • the cover layer may be a single layer or, for example, formed of a plurality of layers, such as an inner cover layer and an outer cover layer.
  • the inventive cores may have a hardness gradient defined by hardness measurements made at the surface of the inner core (or outer core layer) and radially inward towards the center of the inner core, typically at 2-mm increments.
  • the terms “negative” and “positive” refer to the result of subtracting the hardness value at the innermost portion of the component being measured (e.g., the center of a solid core or an inner core in a dual core construction; the inner surface of a core layer; etc.) from the hardness value at the outer surface of the component being measured (e.g., the outer surface of a solid core; the outer surface of an inner core in a dual core; the outer surface of an outer core layer in a dual core, etc.).
  • the core layers is made from a composition including at least one thermoset base rubber, such as a polybutadiene rubber, cured with at least one peroxide and at least one reactive co-agent, which can be a metal salt of an unsaturated carboxylic acid, such as acrylic acid or methacrylic acid, a non-metallic coagent, or mixtures thereof.
  • a suitable antioxidant is included in the composition.
  • An optional soft and fast agent (and sometimes a cis-to-trans catalyst), such as an organosulfur or metal-containing organosulfur compound, can also be included in the core formulation
  • ingredients that are known to those skilled in the art may be used, and are understood to include, but not be limited to, density-adjusting fillers, process aides, plasticizers, blowing or foaming agents, sulfur accelerators, and/or non-peroxide radical sources.
  • the base thermoset rubber which can be blended with other rubbers and polymers, typically includes a natural or synthetic rubber.
  • a preferred base rubber is 1,4-polybutadiene having a cis structure of at least 40%, preferably greater than 80%, and more preferably greater than 90%.
  • Examples of desirable polybutadiene rubbers include BUNA® CB22 and BUNA® CB23, commercially available from LANXESS Corporation; UBEPOL® 360L and UBEPOL® 150L and UBEPOL-BR rubbers, commercially available from UBE Industries, Ltd.
  • KINEX® 7245 and KINEX® 7265 commercially available from Goodyear of Akron, Ohio
  • Europrene® NEOCIS® BR 40 and BR 60 commercially available from Polimeri Europa
  • BR 01, BR 730, BR 735, BR 11, and BR 51 commercially available from Japan Synthetic Rubber Co., Ltd
  • PETROFLEX® BRNd-40 PETROFLEX® BRNd-40
  • KARBOCHEM® ND40, ND45, and ND60 commercially available from Karbochem.
  • the base rubber may also comprise high or medium Mooney viscosity rubber, or blends thereof.
  • a “Mooney” unit is a unit used to measure the plasticity of raw or unvulcanized rubber.
  • the plasticity in a “Mooney” unit is equal to the torque, measured on an arbitrary scale, on a disk in a vessel that contains rubber at a temperature of 100° C. and rotates at two revolutions per minute.
  • the measurement of Mooney viscosity is defined according to ASTM D-1646.
  • the Mooney viscosity range is preferably greater than about 40, more preferably in the range from about 40 to about 80 and more preferably in the range from about 40 to about 60.
  • Polybutadiene rubber with higher Mooney viscosity may also be used, so long as the viscosity of the polybutadiene does not reach a level where the high viscosity polybutadiene clogs or otherwise adversely interferes with the manufacturing machinery. It is contemplated that polybutadiene with viscosity less than 65 Mooney can be used with the present invention.
  • golf ball cores made with mid- to high-Mooney viscosity polybutadiene material exhibit increased resiliency (and, therefore, distance) without increasing the hardness of the ball.
  • Such cores are soft, i.e., compression less than about 60 and more specifically in the range of about 50-55. Cores with compression in the range of from about 30 about 50 are also within the range of this preferred embodiment.
  • suitable mid- to high-Mooney viscosity polybutadiene include Bayer AG CB23 (Nd-catalyzed), which has a Mooney viscosity of around 50 and is a highly linear polybutadiene, and Shell 1220 (Co-catalyzed).
  • the polybutadiene can also be mixed with other elastomers known in the art, such as other polybutadiene rubbers, natural rubber, styrene butadiene rubber, and/or isoprene rubber in order to further modify the properties of the core.
  • the amounts of other constituents in the core composition are typically based on 100 parts by weight of the total elastomer mixture.
  • the base rubber comprises a Nd-catalyzed polybutadiene, a rare earth-catalyzed polybutadiene rubber, or blends thereof
  • the polybutadiene can also be mixed with other elastomers known in the art such as natural rubber, polyisoprene rubber and/or styrene-butadiene rubber in order to modify the properties of the core.
  • Other suitable base rubbers include thermosetting materials such as, ethylene propylene diene monomer rubber, ethylene propylene rubber, butyl rubber, halobutyl rubber, hydrogenated nitrile butadiene rubber, nitrile rubber, and silicone rubber.
  • Thermoplastic elastomers many also be used to modify the properties of the core layers, or the uncured core layer stock by blending with the base thermoset rubber.
  • TPEs include natural or synthetic balata, or high trans-polyisoprene, high trans-polybutadiene, or any styrenic block copolymer, such as styrene ethylene butadiene styrene, styrene-isoprene-styrene, etc., a metallocene or other single-site catalyzed polyolefin such as ethylene-octene, or ethylene-butene, or thermoplastic polyurethanes (TPU), including copolymers, e.g.
  • thermoset rubbers of the present invention include PEBAX®, which is believed to comprise polyether amide copolymers, HYTREL®, which is believed to comprise polyether ester copolymers, thermoplastic urethane, and KRATON®, which is believed to comprise styrenic block copolymers elastomers.
  • PEBAX® which is believed to comprise polyether amide copolymers
  • HYTREL® which is believed to comprise polyether ester copolymers
  • thermoplastic urethane thermoplastic urethane
  • KRATON® which is believed to comprise styrenic block copolymers elastomers.
  • Any of the TPEs or TPUs above may also contain functionality suitable for grafting, including maleic acid or maleic anhydride.
  • Additional polymers may also optionally be incorporated into the base rubber.
  • examples include, but are not limited to, thermoset elastomers such as core regrind, thermoplastic vulcanizate, copolymeric ionomer, terpolymeric ionomer, polycarbonate, polyamide, copolymeric polyamide, polyesters, polyvinyl alcohols, acrylonitrile-butadiene-styrene copolymers, polyarylate, polyacrylate, polyphenylene ether, impact-modified polyphenylene ether, high impact polystyrene, diallyl phthalate polymer, styrene-acrylonitrile polymer (SAN) (including olefin-modified SAN and acrylonitrile-styrene-acrylonitrile polymer), styrene-maleic anhydride copolymer, styrenic copolymer, functionalized styrenic copolymer, functionalized styrenic
  • Suitable polyamides for use as an additional polymeric material in compositions within the scope of the present invention also include resins obtained by: (1) polycondensation of (a) a dicarboxylic acid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid, isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) a diamine, such as ethylenediamine, tetramethylenediamine, pentamethylenediamine, hexamethylenediamine, or decamethylenediamine, 1,4-cyclohexanediamine, or m-xylylenediamine; (2) a ring-opening polymerization of cyclic lactam, such as C-caprolactam or ⁇ -laurolactam; (3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproic acid, 9-aminononanoic acid, 11-aminoundecan
  • Suitable peroxide initiating agents include dicumyl peroxide; 2,5-dimethyl-2,5-di(t-butylperoxy)hexane; 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne; 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; 2,2′-bis(t-butylperoxy)-di-iso-propylbenzene; 1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl 4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide; n-butyl 4,4′-bis(butylperoxy)valerate; di-t-butyl peroxide; or 2,5-di-(t-butylperoxy)-2,5-dimethyl hexan
  • the rubber composition includes from about 0.25 to about 5.0 parts by weight peroxide per 100 parts by weight rubber (phr), more preferably 0.5 phr to 3 phr, most preferably 0.5 phr to 1.5 phr.
  • the peroxide is present in an amount of about 0.8 phr. These ranges of peroxide are given assuming the peroxide is 100% active, without accounting for any carrier that might be present. Because many commercially available peroxides are sold along with a carrier compound, the actual amount of active peroxide present must be calculated.
  • peroxide initiating agents include DICUPTM family of dicumyl peroxides (including DICUPTM R, DICUPTM 40C and DICUPTM 40KE) available from Crompton (Geo Specialty Chemicals). Similar initiating agents are available from AkroChem, Lanxess, Flexsys/Harwick and R.T. Vanderbilt.
  • Another commercially-available and preferred initiating agent is TRIGONOXTM 265-50B from Akzo Nobel, which is a mixture of 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane and di(2-t-butylperoxyisopropyl)benzene.
  • TRIGONOXTM peroxides are generally sold on a carrier compound.
  • Suitable reactive co-agents include, but are not limited to, metal salts of diacrylates, dimethacrylates, and monomethacrylates suitable for use in this invention include those wherein the metal is zinc, magnesium, calcium, barium, tin, aluminum, lithium, sodium, potassium, iron, zirconium, and bismuth.
  • Zinc diacrylate (ZDA) is preferred, but the present invention is not limited thereto.
  • ZDA provides golf balls with a high initial velocity.
  • the ZDA can be of various grades of purity. For the purposes of this invention, the lower the quantity of zinc stearate present in the ZDA the higher the ZDA purity. ZDA containing less than about 10% zinc stearate is preferable. More preferable is ZDA containing about 4-8% zinc stearate.
  • Suitable, commercially available zinc diacrylates include those from Sartomer Co.
  • the preferred concentrations of ZDA that can be used are about 10 phr to about 40 phr, more preferably 20 phr to about 35 phr, most preferably 25 phr to about 35 phr.
  • the reactive co-agent is present in an amount of about 29 phr to about 31 phr.
  • Additional preferred co-agents that may be used alone or in combination with those mentioned above include, but are not limited to, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, and the like. It is understood by those skilled in the art, that in the case where these co-agents may be liquids at room temperature, it may be advantageous to disperse these compounds on a suitable carrier to promote ease of incorporation in the rubber mixture.
  • Antioxidants are compounds that inhibit or prevent the oxidative breakdown of elastomers, and/or inhibit or prevent reactions that are promoted by oxygen radicals.
  • Some exemplary antioxidants that may be used in the present invention include, but are not limited to, quinoline type antioxidants, amine type antioxidants, and phenolic type antioxidants.
  • a preferred antioxidant is 2,2′-methylene-bis-(4-methyl-6-t-butylphenol) available as VANOX® MBPC from R.T. Vanderbilt.
  • Other polyphenolic antioxidants include VANOX® T, VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290.
  • Suitable antioxidants include, but are not limited to, alkylene-bis-alkyl substituted cresols, such as 4,4′-methylene-bis(2,5-xylenol); 4,4′-ethylidene-bis-(6-ethyl-m-cresol); 4,4′-butylidene-bis-(6-t-butyl-m-cresol); 4,4′-decylidene-bis-(6-methyl-m-cresol); 4,4′-methylene-bis-(2-amyl-m-cresol); 4,4′-propylidene-bis-(5-hexyl-m-cresol); 3,3′-decylidene-bis-(5-ethyl-p-cresol); 2,2′-butylidene-bis-(3-n-hexyl-p-cresol); 4,4′-(2-butylidene)-bis-(6-t-butyl-m-cresol); 3,3′-4
  • antioxidants include, but are not limited to, substituted phenols, such as 2-tert-butyl-4-methoxyphenol; 3-tert-butyl-4-methoxyphenol; 3-tert-octyl-4-methoxyphenol; 2-methyl-4-methoxyphenol; 2-stearyl-4-n-butoxyphenol; 3-t-butyl-4-stearyloxyphenol; 3-lauryl-4-ethoxyphenol; 2,5-di-t-butyl-4-methoxyphenol; 2-methyl-4-methoxyphenol; 2-(1-methycyclohexyl)-4-methoxyphenol; 2-t-butyl-4-dodecyloxyphenol; 2-(1-methylbenzyl)-4-methoxyphenol; 2-t-octyl-4-methoxyphenol; methyl gallate; n-propyl gallate; n-butyl gallate; lauryl gallate; myristyl gallate; stearyl gallate; 2,4,5-trihydroxy
  • antioxidants include, but are not limited to, alkylene bisphenols, such as 4,4′-butylidene bis(3-methyl-6-t-butyl phenol); 2,2-butylidene bis(4,6-dimethyl phenol); 2,2′-butylidene bis(4-methyl-6-t-butyl phenol); 2,2′-butylidene bis(4-t-butyl-6-methyl phenol); 2,2′-ethylidene bis(4-methyl-6-t-butylphenol); 2,2′-methylene bis(4,6-dimethyl phenol); 2,2′-methylene bis(4-methyl-6-t-butyl phenol); 2,2′-methylene bis(4-ethyl-6-t-butyl phenol); 4,4′-methylene bis(2,6-di-t-butyl phenol); 4,4′-methylene bis(2-methyl-6-t-butyl phenol); 4,4′-methylene bis(2,6-dimethyl phenol);
  • Suitable antioxidants further include, but are not limited to, alkylene trisphenols, such as 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methyl benzyl)-4-methyl phenol; 2,6-bis(2′-hydroxy-3′-t-ethyl-5′-butyl benzyl)-4-methyl phenol; and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-propyl benzyl)-4-methyl phenol.
  • alkylene trisphenols such as 2,6-bis(2′-hydroxy-3′-t-butyl-5′-methyl benzyl)-4-methyl phenol; 2,6-bis(2′-hydroxy-3′-t-ethyl-5′-butyl benzyl)-4-methyl phenol; and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-propyl benzyl)-4-methyl phenol.
  • the antioxidant is typically present in an amount of about 0.1 phr to about 5 phr, preferably from about 0.1 phr to about 2 phr, more preferably about 0.1 phr to about 1 phr. In a particularly preferred embodiment, the antioxidant is present in an amount of about 0.4 phr.
  • the antioxidant should be present in an amount to ensure that the hardness gradient of the inventive cores is negative.
  • about 0.2 phr to about 1 phr antioxidant is added to the core layer (inner core or outer core layer) formulation, more preferably, about 0.3 to about 0.8 phr, and most preferably 0.4 to about 0.7 phr.
  • about 0.25 phr to about 1.5 phr of peroxide as calculated at 100% active can be added to the core formulation, more preferably about 0.5 phr to about 1.2 phr, and most preferably about 0.7 phr to about 1.0 phr.
  • the ZDA amount can be varied to suit the desired compression, spin and feel of the resulting golf ball.
  • the cure regime can have a temperature range between from about 290° F. to about 335° F., more preferably about 300° F. to about 325° F., and the stock is held at that temperature for at least about 10 minutes to about 30 minutes.
  • thermoset rubber composition of the present invention may also include an optional soft and fast agent.
  • soft and fast agent means any compound or a blend thereof that that is capable of making a core 1) be softer (lower compression) at constant COR or 2) have a higher COR at equal compression, or any combination thereof, when compared to a core equivalently prepared without a soft and fast agent.
  • the composition of the present invention contains from about 0.05 phr to about 10.0 phr soft and fast agent.
  • the soft and fast agent is present in an amount of about 0.05 phr to about 3.0 phr, preferably about 0.05 phr to about 2.0 phr, more preferably about 0.05 phr to about 1.0 phr. In another embodiment, the soft and fast agent is present in an amount of about 2.0 phr to about 5.0 phr, preferably about 2.35 phr to about 4.0 phr, and more preferably about 2.35 phr to about 3.0 phr.
  • the soft and fast agent is present in an amount of about 5.0 phr to about 10.0 phr, more preferably about 6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about 8.0 phr. In a most preferred embodiment, the soft and fast agent is present in an amount of about 2.6 phr.
  • Suitable soft and fast agents include, but are not limited to, organosulfur or metal-containing organosulfur compounds, an organic sulfur compound, including mono, di, and polysulfides, a thiol, or mercapto compound, an inorganic sulfide compound, a Group VIA compound, or mixtures thereof.
  • the soft and fast agent component may also be a blend of an organosulfur compound and an inorganic sulfide compound.
  • Suitable soft and fast agents of the present invention include, but are not limited to those having the following general formula:
  • R 1 -R 5 can be C 1 -C 8 alkyl groups; halogen groups; thiol groups (—SH), carboxylated groups; sulfonated groups; and hydrogen; in any order; and also pentafluorothiophenol; 2-fluorothiophenol; 3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol; 2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol 2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol; 2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol; 4-chlorotetrafluorothiophenol; pentachlorothiophenol; 2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol; 2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol
  • the halogenated thiophenol compound is pentachlorothiophenol, which is commercially available in neat form or under the tradename STRUKTOL®, a clay-based carrier containing the sulfur compound pentachlorothiophenol loaded at 45 percent (correlating to 2.4 parts PCTP).
  • STRUKTOL® is commercially available from Struktol Company of America of Stow, Ohio.
  • PCTP is commercially available in neat form from eChinachem of San Francisco, Calif. and in the salt form from eChinachem of San Francisco, Calif.
  • the halogenated thiophenol compound is the zinc salt of pentachlorothiophenol, which is commercially available from eChinachem of San Francisco, Calif.
  • organosulfur compound(s) refers to any compound containing carbon, hydrogen, and sulfur, where the sulfur is directly bonded to at least 1 carbon.
  • sulfur compound means a compound that is elemental sulfur, polymeric sulfur, or a combination thereof.
  • elemental sulfur refers to the ring structure of S 8 and that “polymeric sulfur” is a structure including at least one additional sulfur relative to elemental sulfur.
  • soft and fast agents that are also believed to be cis-to-trans catalysts
  • soft and fast agents include, but are not limited to, 4,4′-diphenyl disulfide; 4,4′-ditolyl disulfide; 2,2′-benzamido diphenyl disulfide; bis(2-aminophenyl)disulfide; bis(4-aminophenyl)disulfide; bis(3-aminophenyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide; 2,2′-bis(3-aminonaphthyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide; 2,2′-bis(5-aminonaphthyl)disulfide; 2,2′-bis(6-aminonaphthyl)disulfide; 2,2′-bis(7
  • Preferred organosulfur components include 4,4′-diphenyl disulfide, 4,4′-ditolyl disulfide, or 2,2′-benzamido diphenyl disulfide, or a mixture thereof.
  • a more preferred organosulfur component includes 4,4′-ditolyl disulfide.
  • metal-containing organosulfur components can be used according to the invention. Suitable metal-containing organosulfur components include, but are not limited to, cadmium, copper, lead, and tellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, and dimethyldithiocarbamate, or mixtures thereof.
  • Suitable substituted or unsubstituted aromatic organic components that do not include sulfur or a metal include, but are not limited to, 4,4′-diphenyl acetylene, azobenzene, or a mixture thereof.
  • the aromatic organic group preferably ranges in size from C 6 to C 20 , and more preferably from C 6 to C 10 .
  • Suitable inorganic sulfide components include, but are not limited to titanium sulfide, manganese sulfide, and sulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper, selenium, yttrium, zinc, tin, and bismuth.
  • a substituted or unsubstituted aromatic organic compound is also suitable as a soft and fast agent.
  • Suitable substituted or unsubstituted aromatic organic components include, but are not limited to, components having the formula (R 1 ) x —R 3 -M-R 4 —(R 2 ) y , wherein R 1 and R 2 are each hydrogen or a substituted or unsubstituted C 1-20 linear, branched, or cyclic alkyl, alkoxy, or alkylthio group, or a single, multiple, or fused ring C 6 to C 24 aromatic group; x and y are each an integer from 0 to 5; R 3 and R 4 are each selected from a single, multiple, or fused ring C 6 to C 24 aromatic group; and M includes an azo group or a metal component.
  • R 3 and R 4 are each preferably selected from a C 6 to C 10 aromatic group, more preferably selected from phenyl, benzyl, naphthyl, benzamido, and benzothiazyl.
  • R 1 and R 2 are each preferably selected from a substituted or unsubstituted C 1-10 linear, branched, or cyclic alkyl, alkoxy, or alkylthio group or a C 6 to C 10 aromatic group.
  • substitution may include one or more of the following substituent groups: hydroxy and metal salts thereof; mercapto and metal salts thereof; halogen; amino, nitro, cyano, and amido; carboxyl including esters, acids, and metal salts thereof; silyl; acrylates and metal salts thereof; sulfonyl or sulfonamide; and phosphates and phosphites.
  • M is a metal component, it may be any suitable elemental metal available to those of ordinary skill in the art. Typically, the metal will be a transition metal, although preferably it is tellurium or selenium.
  • the aromatic organic compound is substantially free of metal, while in another embodiment the aromatic organic compound is completely free of metal.
  • the soft and fast agent can also include a Group VIA component.
  • Elemental sulfur and polymeric sulfur are commercially available from Elastochem, Inc. of Chardon, Ohio.
  • Exemplary sulfur catalyst compounds include PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymeric sulfur, each of which is available from Elastochem, Inc.
  • An exemplary tellurium catalyst under the tradename TELLOY® and an exemplary selenium catalyst under the tradename VANDEX® are each commercially available from RT Vanderbilt.
  • soft and fast agents include, but are not limited to, hydroquinones, benzoquinones, quinhydrones, catechols, and resorcinols.
  • Suitable hydroquinone compounds include compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are hydrogen; halogen; alkyl; carboxyl; metal salts thereof, and esters thereof; acetate and esters thereof; formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • hydroquinone compounds include, but are not limited to, hydroquionone; tetrachlorohydroquinone; 2-chlorohydroquionone; 2-bromohydroquinone; 2,5-dichlorohydroquinone; 2,5-dibromohydroquinone; tetrabromohydroquinone; 2-methylhydroquinone; 2-t-butylhydroquinone; 2,5-di-t-amylhydroquinone; and 2-(2-chlorophenyl)hydroquinone hydrate.
  • hydroquinone compounds include compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are a metal salt of a carboxyl; acetate and esters thereof; hydroxy; a metal salt of a hydroxy; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • Suitable benzoquinone compounds include compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are hydrogen; halogen; alkyl; carboxyl; metal salts thereof, and esters thereof; acetate and esters thereof; formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • benzoquinone compounds include one or more compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are a metal salt of a carboxyl; acetate and esters thereof; hydroxy; a metal salt of a hydroxy; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • Suitable quinhydrones include one or more compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 are hydrogen; halogen; alkyl; carboxyl; metal salts thereof, and esters thereof; acetate and esters thereof; formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 are a metal salt of a carboxyl; acetate and esters thereof; hydroxy; a metal salt of a hydroxy; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • Suitable catechols include one or more compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are hydrogen; halogen; alkyl; carboxyl; metal salts thereof, and esters thereof; acetate and esters thereof; formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • Suitable resorcinols include one or more compounds represented by the following formula, and hydrates thereof:
  • each R 1 , R 2 , R 3 , and R 4 are hydrogen; halogen; alkyl; carboxyl; metal salts thereof, and esters thereof; acetate and esters thereof; formyl; acyl; acetyl; halogenated carbonyl; sulfo and esters thereof; halogenated sulfonyl; sulfino; alkylsulfinyl; carbamoyl; halogenated alkyl; cyano; alkoxy; hydroxy and metal salts thereof; amino; nitro; aryl; aryloxy; arylalkyl; nitroso; acetamido; or vinyl.
  • Fillers may also be added to the thermoset rubber composition of the core to adjust the density of the composition, up or down.
  • fillers include materials such as tungsten, zinc oxide, barium sulfate, silica, calcium carbonate, zinc carbonate, metals, metal oxides and salts, regrind (recycled core material typically ground to about 30 mesh particle), high-Mooney-viscosity rubber regrind, trans-regrind core material (recycled core material containing high trans-isomer of polybutadiene), and the like.
  • regrind recycled core material typically ground to about 30 mesh particle
  • high-Mooney-viscosity rubber regrind high-Mooney-viscosity rubber regrind
  • trans-regrind core material recycled core material containing high trans-isomer of polybutadiene
  • the amount of trans-isomer is preferably between about 10% and about 60%.
  • the core comprises polybutadiene having a cis-isomer content of greater than about 95% and trans-regrind core material (already vulcanized) as a filler.
  • trans-regrind core material any particle size trans-regrind core material is sufficient, but is preferably less than about 125 ⁇ m.
  • Fillers added to one or more portions of the golf ball typically include processing aids or compounds to affect rheological and mixing properties, density-modifying fillers, tear strength, or reinforcement fillers, and the like.
  • the fillers are generally inorganic, and suitable fillers include numerous metals or metal oxides, such as zinc oxide and tin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate, barium carbonate, clay, tungsten, tungsten carbide, an array of silicas, and mixtures thereof.
  • Fillers may also include various foaming agents or blowing agents which may be readily selected by one of ordinary skill in the art.
  • Fillers may include polymeric, ceramic, metal, and glass microspheres may be solid or hollow, and filled or unfilled.
  • Fillers are typically also added to one or more portions of the golf ball to modify the density thereof to conform to uniform golf ball standards. Fillers may also be used to modify the weight of the center or at least one additional layer for specialty balls, e.g., a lower weight ball is preferred for a player having a low swing speed.
  • regrind recycled core material typically ground to about 30 mesh particle
  • the polybutadiene and/or any other base rubber or elastomer system may also be foamed, or filled with hollow microspheres or with expandable microspheres which expand at a set temperature during the curing process to any low specific gravity level.
  • Other ingredients such as sulfur accelerators, e.g., tetra methylthiuram di, tri, or tetrasulfide, and/or metal-containing organosulfur components may also be used according to the invention.
  • Suitable metal-containing organosulfur accelerators include, but are not limited to, cadmium, copper, lead, and tellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, and dimethyldithiocarbamate, or mixtures thereof.
  • Other ingredients such as processing aids e.g., fatty acids and/or their metal salts, processing oils, dyes and pigments, as well as other additives known to one skilled in the art may also be used in the present invention in amounts sufficient to achieve the purpose for which they are typically used.
  • the present invention is preferably a golf ball including a “dual core,” in which both the inner core and outer core layer have a “negative” hardness gradient, optionally a zero gradient.
  • a “low spin” embodiment the inner surface of the outer core layer is harder than the outer surface of the inner core.
  • a “high spin” embodiment the inner surface of the outer core layer is softer than the outer surface of the inner core.
  • the hardness of the inner surface of the outer core layer is substantially identical to the hardness of the outer surface of the inner core, effectively providing a continuous “negative” gradient extending from the outer surface of the outer core layer to the center of the solid center.
  • the hardness of the inner core ranges from 30 Shore C to 80 Shore C, more preferably 40 Shore C to 75 Shore C, most preferably 45 Shore C to 70 Shore C.
  • the hardness of the outer core layer ranges from 60 Shore C to 95 Shore C, more preferably 60 Shore C to 90 Shore C, most preferably 65 Shore C to 80 Shore C.
  • the hardness of the inner core ranges from 60 Shore C to 95 Shore C, more preferably 60 Shore C to 90 Shore C, most preferably 65 Shore C to 80 Shore C.
  • the hardness of the outer core layer ranges from 30 Shore C to 80 Shore C, more preferably 40 Shore C to 75 Shore C, most preferably 45 Shore C to 70 Shore C.
  • the interface i.e., the area where the two components meet
  • the ranges provided for either the “low spin” or “high spin” embodiments are sufficient, as long as the “negative” hardness gradient is maintained and the hardness value at the inner surface of the outer core layer is roughly the same as the hardness value at the outer surface of the inner core.
  • FIGS. 2 and 3 Representative graphs depicting the hardness regions in which the “negative” hardness gradients disclosed herein can reside are shown in FIGS. 2 and 3 .
  • the “negative” gradients particularly in the above embodiments, can have any slope (i.e., steep, shallow, or substantially flat).
  • a point or plurality of points measured along the “negative” gradient may be above or below a line fit through the gradient and its outermost and innermost hardness values.
  • the hardest point along a particular “negative” gradient may be higher than the value at the innermost portion of the inner core (the geometric center) or outer core layer (the inner surface)—as long as the outermost point (i.e., the outer surface of the inner core) is about the same or lower than the innermost point (i.e., the geometric center of the inner core), the “negative” gradient remains intact.
  • the inner core preferably has an outer diameter of about 1.00 inch and the core (the combination of the inner core and the outer core layer) preferably has an outer diameter of about 1.53 inches.
  • Any cover material listed above would be suitable and an inner cover may or may not be present.
  • an inner cover layer is present and it an ionomer-based material, such as a highly-neutralized ionomer, and preferably the outer cover is formed from a urethane or urea material.
  • the inner core center hardness is about 42 Shore C and the surface hardness is about 37 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 79 Shore C and the outer surface has a hardness of about 73 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 60 and the COR is about 0.790.
  • the antioxidant (AO):initiator ratio of the inner core is about 0.5 and the ZDA level is about 8-10 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.4 and the ZDA level is about 32-34 phr.
  • the cure temperature and time for both the inner core and outer core layer is about 315° F. for 11 min.
  • the inner core center hardness is about 56 Shore C and the surface hardness is about 55 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 89 Shore C and the outer surface has a hardness of about 82 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 70 and the COR is about 0.805.
  • the antioxidant:initiator ratio of the inner core is about 0.5 and the ZDA level is about 10-12 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.5 and the ZDA level is about 34-36 phr.
  • the cure temperature and time for both the inner core and outer core layer is about 320° F. for 11 min.
  • the inner core center hardness is about 46 Shore C and the surface hardness is about 44 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 62 Shore C and the outer surface has a hardness of about 58 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 65 and the COR is about 0.800.
  • the antioxidant:initiator ratio of the inner core is about 0.4 and the ZDA level is about 8-10 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.3 and the ZDA level is about 26-28 phr.
  • the cure temperature and time for both the inner core and outer core layer is about 315° F. for 11 min.
  • the inner core preferably has an outer diameter of about 1.00 inch and the core (the combination of the inner core and the outer core layer) preferably has an outer diameter of about 1.53 inches.
  • the inner core center hardness is about 74 Shore C and the surface hardness is about 71 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 68 Shore C and the outer surface has a hardness of about 63 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 68 and the COR is about 0.790.
  • the antioxidant:initiator ratio of the inner core is about 0.5 and the ZDA level is about 28-30 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.4 and the ZDA level is about 12-14 phr.
  • the cure temperature and time for the inner core is about 320° F. for 14 min, and for the outer core layer about 320° F. for 11 min.
  • the inner core center hardness is about 86 Shore C and the surface hardness is about 83 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 61 Shore C and the outer surface has a hardness of about 57 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 74 and the COR is about 0.800.
  • the antioxidant:initiator ratio of the inner core is about 0.4 and the ZDA level is about 33-35 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.5 and the ZDA level is about 11-13 phr.
  • the cure temperature and time for the inner core is about 320° F. for 14 min, and for the outer core layer about 315° F. for 11 min.
  • the inner core center hardness is about 65 Shore C and the surface hardness is about 61 Shore C, exhibiting the “negative” hardness gradient of the present invention.
  • the inner surface of the outer core layer has a hardness of about 52 Shore C and the outer surface has a hardness of about 49 Shore C, again exhibiting the “negative” gradient of the invention.
  • the Atti compression of this core is preferably about 62 and the COR is about 0.785.
  • the antioxidant:initiator ratio of the inner core is about 0.5 and the ZDA level is about 25-27 phr.
  • the antioxidant:initiator ratio of the outer core layer is about 0.5 and the ZDA level is about 9-11 phr.
  • the cure temperature and time for the inner core is about 315° F. for 14 min, and for the outer core layer about 315° F. for 11 min.
  • Alternative embodiments include a golf ball where the hardness of the outer surface of the inner core generally ranges from 42 Shore C to 60 Shore C and the hardness of the geometric center of the inner core generally ranges from 52 Shore C to 65 Shore C such that the “positive hardness gradient” has a magnitude of about 0 to ⁇ 10.
  • the hardness of the outer surface of the outer core layer generally ranges from 62 Shore C to 89 Shore C and the hardness of the inner surface of the outer core layer generally ranges from 58 Shore C to 82 Shore C such that the “negative hardness gradient” has a magnitude of about 10 to 20.
  • the hardness of the outer surface of the inner core may range from 61 Shore C to 83 Shore C and the hardness of the geometric center of the inner core may range from 65 Shore C to 86 Shore C such that the “positive hardness gradient” has a magnitude of about 0 to ⁇ 10.
  • the hardness of the outer surface of the outer core layer generally ranges from 52 Shore C to 68 Shore C and the hardness of the inner surface of the outer core layer generally ranges from 49 Shore C to 63 Shore C such that the “negative hardness gradient” has a magnitude of about 10 to 20.
  • alternative embodiments include those having an inner core having an outer diameter of about 0.250 inches to about 1.550 inches, preferably about 0.500 inches to about 1.500 inches, and more preferably about 0.750 inches to about 1.400 inches.
  • the inner core has an outer diameter of about 1.000 inch, 1.200 inches, or 1.300 inches, with a most preferred outer diameter being 1.130 inches.
  • the outer core layer should have an outer diameter (the entire dual core) of about 1.30 inches to about 1.620 inches, preferably 1.400 inches to about 1.600 inches, and more preferably about 1.500 inches to about 1.590 inches.
  • the outer core layer has an outer diameter of about 1.510 inches, 1.530 inches, or most preferably 1.550 inches.
  • the surface hardness of a core is obtained from the average of a number of measurements taken from opposing hemispheres of a core, taking care to avoid making measurements on the parting line of the core or on surface defects, such as holes or protrusions.
  • Hardness measurements are made pursuant to ASTM D-2240 “Indentation Hardness of Rubber and Plastic by Means of a Durometer.” Because of the curved surface of a core, care must be taken to insure that the core is centered under the durometer indentor before a surface hardness reading is obtained.
  • a calibrated, digital durometer capable of reading to 0.1 hardness units is used for all hardness measurements and is set to take hardness readings at 1 second after the maximum reading is obtained. The digital durometer must be attached to, and its foot made parallel to, the base of an automatic stand, such that the weight on the durometer and attack rate conform to ASTM D-2240.
  • the core is gently pressed into a hemispherical holder having an internal diameter approximately slightly smaller than the diameter of the core, such that the core is held in place in the hemispherical portion of the holder while concurrently leaving the geometric central plane of the core exposed.
  • the core is secured in the holder by friction, such that it will not move during the cutting and grinding steps, but the friction is not so excessive that distortion of the natural shape of the core would result.
  • the core is secured such that the parting line of the core is roughly parallel to the top of the holder.
  • the diameter of the core is measured 90 degrees to this orientation prior to securing.
  • a measurement is also made from the bottom of the holder to the top of the core to provide a reference point for future calculations.
  • the remainder of the core, still in the holder, is secured to the base plate of a surface grinding machine.
  • the exposed ‘rough’ core surface is ground to a smooth, flat surface, revealing the geometric center of the core, which can be verified by measuring the height of the bottom of the holder to the exposed surface of the core, making sure that exactly half of the original height of the core, as measured above, has been removed to within ⁇ 0.004 inches.
  • the center of the core is found with a center square and carefully marked and the hardness is measured at the center mark.
  • Hardness measurements at any distance from the center of the core may be measured by drawing a line radially outward from the center mark, and measuring and marking the distance from the center, typically in 2-mm increments. All hardness measurements performed on the plane passing through the geometric center are performed while the core is still in the holder and without having disturbed its orientation, such that the test surface is constantly parallel to the bottom of the holder.
  • the hardness difference from any predetermined location on the core is calculated as the average surface hardness minus the hardness at the appropriate reference point, e.g., at the center of the core for single, solid core, such that a core surface softer than its center will have a negative hardness gradient.
  • Example 1 the surface is 10 Shore C points lower than the center hardness and 12 Shore C points lower than the hardest point in the core.
  • the surface is 5 Shore C points lower than the center hardness and 8 Shore C points lower than the hardest point in the core.
  • Example 2 the center and surface hardness values are equal and the softest point in the core is 10 Shore C points lower than the surface.
  • the cure temperatures are varied from 305° F. to 320° F. and cure times are varied from 11 to 16 minutes.
  • the core compositions of examples 1 and 2 are identical, and only the cure cycle is changed.
  • the amount of antioxidant is identical to examples 1 and 2, but other ingredients are varied as well the cure cycle. Additionally, the ratio of antioxidant to initiator varies from 0.50 to 0.57 from example 1 and 2 to example 3.
  • the ratio of antioxidant to initiator is one factor to control the surface hardness of the cores.
  • the data shown in TABLE 2 shows that hardness gradient is at least, but not limited to, a function of the amount of antioxidant and peroxide, their ratio, and the cure cycle. It should be noted that higher antioxidant also requires higher peroxide initiator to maintain the desired compression.
  • FIG. 1 cores of Comparative Examples 1-3 are compared to the inventive cores.
  • the core of Comparative Example 1 whose composition is shown in TABLE 1 was cured using a conventional cure cycle, with a cure temperature of 350° F. and a cure time of 11 minutes.
  • the inventive cores were produced using cure cycles of 305° F. for 14 minutes, 315° F. for 11 minutes and 320° F. for 16 minutes.
  • the hardness gradients of these cores were measured and the following observations can be made.
  • a conventional hard surface to soft center gradient can be clearly seen.
  • the gradients for inventive cores follow substantially the same shape as one another.
  • the hardness of the core at the surface is at most about the same as or substantially less than the hardness of the core at the center.
  • the center hardness of the core may not be the hardest point in the core, but in all cases, it is preferred that it is at least equal to or harder than the surface.
  • the lowest hardness anywhere in the core does not have to occur at the surface. In some embodiments, the lowest hardness value occurs within about the outer 6 mm of the core surface. However, the lowest hardness value within the core can occur at any point from the surface, up to, but not including the center, as long as the surface hardness is still equal to, or less than the hardness of the center. It should be noted that in the present invention the formulation is the same throughout the core, or core layer, and no surface treatment is applied to the core to obtain the preferred surface hardness.
  • inventive golf ball may be formed from a variety of differing and conventional cover materials (both intermediate layer(s) and outer cover layer), preferred cover materials include, but are not limited to:
  • Suitable polyurethane compositions comprise a reaction product of at least one polyisocyanate and at least one curing agent.
  • the curing agent can include, for example, one or more polyamines, one or more polyols, or a combination thereof.
  • the polyisocyanate can be combined with one or more polyols to form a prepolymer, which is then combined with the at least one curing agent.
  • the polyols described herein are suitable for use in one or both components of the polyurethane material, i.e., as part of a prepolymer and in the curing agent.
  • Suitable polyurethanes are described in U.S. Patent Application Publication No. 2005/0176523, which is incorporated by reference in its entirety.
  • polyisocyanates include, but are not limited to, 4,4′-diphenylmethane diisocyanate (MDI); polymeric MDI; carbodiimide-modified liquid MDI; 4,4′-dicyclohexylmethane diisocyanate (H 12 MDI); p-phenylene diisocyanate (PPDI); m-phenylene diisocyanate (MPDI); toluene diisocyanate (TDI); 3,3′-dimethyl-4,4′-biphenylene diisocyanate; isophoronediisocyanate; 1,6-hexamethylene diisocyanate (HDI); naphthalene diisocyanate; xylene diisocyanate; p-tetramethylxylene diisocyanate; m-tetramethylxylene diisocyanate; ethylene diis
  • Polyisocyanates are known to those of ordinary skill in the art as having more than one isocyanate group, e.g., di-isocyanate, tri-isocyanate, and tetra-isocyanate.
  • the polyisocyanate includes MDI, PPDI, TDI, or a mixture thereof, and more preferably, the polyisocyanate includes MDI.
  • MDI includes 4,4′-diphenylmethane diisocyanate, polymeric MDI, carbodiimide-modified liquid MDI, and mixtures thereof and, additionally, that the diisocyanate employed may be “low free monomer,” understood by one of ordinary skill in the art to have lower levels of “free” monomer isocyanate groups, typically less than about 0.1% free monomer isocyanate groups.
  • low free monomer diisocyanates include, but are not limited to Low Free Monomer MDI, Low Free Monomer TDI, and Low Free Monomer PPDI.
  • the at least one polyisocyanate should have less than about 14% unreacted NCO groups.
  • the at least one polyisocyanate has no greater than about 8.0% NCO, more preferably no greater than about 7.8%, and most preferably no greater than about 7.5% NCO with a level of NCO of about 7.2 or 7.0, or 6.5% NCO commonly used.
  • any polyol available to one of ordinary skill in the art is suitable for use according to the invention.
  • Exemplary polyols include, but are not limited to, polyether polyols, hydroxy-terminated polybutadiene (including partially/fully hydrogenated derivatives), polyester polyols, polycaprolactone polyols, and polycarbonate polyols.
  • the polyol includes polyether polyol. Examples include, but are not limited to, polytetramethylene ether glycol (PTMEG), polyethylene propylene glycol, polyoxypropylene glycol, and mixtures thereof.
  • PTMEG polytetramethylene ether glycol
  • the hydrocarbon chain can have saturated or unsaturated bonds and substituted or unsubstituted aromatic and cyclic groups.
  • the polyol of the present invention includes PTMEG.
  • polyester polyols are included in the polyurethane material.
  • Suitable polyester polyols include, but are not limited to, polyethylene adipate glycol; polybutylene adipate glycol; polyethylene propylene adipate glycol; o-phthalate-1,6-hexanediol; poly(hexamethylene adipate)glycol; and mixtures thereof.
  • the hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups.
  • polycaprolactone polyols are included in the materials of the invention.
  • Suitable polycaprolactone polyols include, but are not limited to, 1,6-hexanediol-initiated polycaprolactone, diethylene glycol initiated polycaprolactone, trimethylol propane initiated polycaprolactone, neopentyl glycol initiated polycaprolactone, 1,4-butanediol-initiated polycaprolactone, and mixtures thereof.
  • the hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups.
  • polycarbonate polyols are included in the polyurethane material of the invention.
  • Suitable polycarbonates include, but are not limited to, polyphthalate carbonate and poly(hexamethylene carbonate)glycol.
  • the hydrocarbon chain can have saturated or unsaturated bonds, or substituted or unsubstituted aromatic and cyclic groups.
  • the molecular weight of the polyol is from about 200 to about 4000.
  • Polyamine curatives are also suitable for use in the polyurethane composition of the invention and have been found to improve cut, shear, and impact resistance of the resultant balls.
  • Preferred polyamine curatives include, but are not limited to, 3,5-dimethylthio-2,4-toluenediamine and isomers thereof; 3,5-diethyltoluene-2,4-diamine and isomers thereof, such as 3,5-diethyltoluene-2,6-diamine; 4,4′-bis-(sec-butylamino)-diphenylmethane; 1,4-bis-(sec-butylamino)-benzene, 4,4′-methylene-bis-(2-chloroaniline); 4,4′-methylene-bis-(3-chloro-2,6-diethylaniline); polytetramethyleneoxide-di-p-aminobenzoate; N,N′-dialkyldiamino diphenyl methane; p,
  • the curing agent of the present invention includes 3,5-dimethylthio-2,4-toluenediamine and isomers thereof, such as ETHACURE® 300, commercially available from Albermarle Corporation of Baton Rouge, La.
  • Suitable polyamine curatives which include both primary and secondary amines, preferably have molecular weights ranging from about 64 to about 2000.
  • At least one of a diol, triol, tetraol, or hydroxy-terminated curatives may be added to the aforementioned polyurethane composition.
  • Suitable diol, triol, and tetraol groups include ethylene glycol; diethylene glycol; polyethylene glycol; propylene glycol; polypropylene glycol; lower molecular weight polytetramethylene ether glycol; 1,3-bis(2-hydroxyethoxy)benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene; 1,3-bis- ⁇ 2-[2-(2-hydroxyethoxy)ethoxy]ethoxy ⁇ benzene; 1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; resorcinol-di-( ⁇ -hydroxyethyl)ether; hydroquinone-di-( ⁇ -hydroxyethyl)ether; and mixtures thereof.
  • Preferred hydroxy-terminated curatives include 1,3-bis(2-hydroxyethoxy)benzene; 1,3-bis-[2-(2-hydroxyethoxy)ethoxy]benzene; 1,3-bis- ⁇ 2-[2-(2-hydroxyethoxy)ethoxy]ethoxy ⁇ benzene; 1,4-butanediol, and mixtures thereof.
  • the hydroxy-terminated curatives have molecular weights ranging from about 48 to 2000. It should be understood that molecular weight, as used herein, is the absolute weight average molecular weight and would be understood as such by one of ordinary skill in the art.
  • Both the hydroxy-terminated and amine curatives can include one or more saturated, unsaturated, aromatic, and cyclic groups. Additionally, the hydroxy-terminated and amine curatives can include one or more halogen groups.
  • the polyurethane composition can be formed with a blend or mixture of curing agents. If desired, however, the polyurethane composition may be formed with a single curing agent.
  • saturated polyurethanes are used to form one or more of the cover layers, preferably the outer cover layer, and may be selected from among both castable thermoset and thermoplastic polyurethanes.
  • the saturated polyurethanes of the present invention are substantially free of aromatic groups or moieties.
  • Saturated polyurethanes suitable for use in the invention are a product of a reaction between at least one polyurethane prepolymer and at least one saturated curing agent.
  • the polyurethane prepolymer is a product formed by a reaction between at least one saturated polyol and at least one saturated diisocyanate.
  • a catalyst may be employed to promote the reaction between the curing agent and the isocyanate and polyol, or the curing agent and the prepolymer.
  • Saturated diisocyanates which can be used include, without limitation, ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate (HDI); 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate; dicyclohexylmethane diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate; 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane; isophorone diisocyanate; methyl cyclohexylene diisocyanate; triisocyanate of HDI; triiso
  • Saturated polyols which are appropriate for use in this invention include without limitation polyether polyols such as polytetramethylene ether glycol and poly(oxypropylene)glycol.
  • Suitable saturated polyester polyols include polyethylene adipate glycol, polyethylene propylene adipate glycol, polybutylene adipate glycol, polycarbonate polyol and ethylene oxide-capped polyoxypropylene diols.
  • Saturated polycaprolactone polyols which are useful in the invention include diethylene glycol-initiated polycaprolactone, 1,4-butanediol-initiated polycaprolactone, 1,6-hexanediol-initiated polycaprolactone; trimethylol propane-initiated polycaprolactone, neopentyl glycol initiated polycaprolactone, and polytetramethylene ether glycol-initiated polycaprolactone.
  • the most preferred saturated polyols are polytetramethylene ether glycol and PTMEG-initiated polycaprolactone.
  • Suitable saturated curatives include 1,4-butanediol, ethylene glycol, diethylene glycol, polytetramethylene ether glycol, propylene glycol; trimethanolpropane; tetra-(2-hydroxypropyl)-ethylenediamine; isomers and mixtures of isomers of cyclohexyldimethylol, isomers and mixtures of isomers of cyclohexane bis(methylamine); triisopropanolamine; ethylene diamine; diethylene triamine; triethylene tetramine; tetraethylene pentamine; 4,4′-dicyclohexylmethane diamine; 2,2,4-trimethyl-1,6-hexanediamine; 2,4,4-trimethyl-1,6-hexanediamine; diethyleneglycol di-(aminopropyl)ether; 4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 1,2-bis-(sec-butyla
  • polystyrene-butadiene-styrene polystyrene-ethylene-propylene-styrene
  • styrene-ethylene-butylene-styrene polystyrene-ethylene-butylene-styrene, and the like, and blends thereof.
  • Thermosetting polyurethanes or polyureas are suitable for the outer cover layers of the golf balls of the present invention.
  • polyurethane can be replaced with or blended with a polyurea material.
  • Polyureas are distinctly different from polyurethane compositions, but also result in desirable aerodynamic and aesthetic characteristics when used in golf ball components.
  • the polyurea-based compositions are preferably saturated in nature.
  • the polyurea compositions of this invention may be formed from the reaction product of an isocyanate and polyamine prepolymer crosslinked with a curing agent.
  • polyurea-based compositions of the invention may be prepared from at least one isocyanate, at least one polyether amine, and at least one diol curing agent or at least one diamine curing agent.
  • polyether amines are particularly suitable for use in the prepolymer.
  • polyether amines refer to at least polyoxyalkyleneamines containing primary amino groups attached to the terminus of a polyether backbone. Due to the rapid reaction of isocyanate and amine, and the insolubility of many urea products, however, the selection of diamines and polyether amines is limited to those allowing the successful formation of the polyurea prepolymers.
  • the polyether backbone is based on tetramethylene, propylene, ethylene, trimethylolpropane, glycerin, and mixtures thereof.
  • Suitable polyether amines include, but are not limited to, methyldiethanolamine; polyoxyalkylenediamines such as, polytetramethylene ether diamines, polyoxypropylenetriamine, and polyoxypropylene diamines; poly(ethylene oxide capped oxypropylene)ether diamines; propylene oxide-based triamines; triethyleneglycoldiamines; trimethylolpropane-based triamines; glycerin-based triamines; and mixtures thereof.
  • the polyether amine used to form the prepolymer is JEFFAMINE® D2000 (manufactured by Huntsman Chemical Co. of Austin, Tex.).
  • the molecular weight of the polyether amine for use in the polyurea prepolymer may range from about 100 to about 5000. In one embodiment, the polyether amine molecular weight is about 200 or greater, preferably about 230 or greater. In another embodiment, the molecular weight of the polyether amine is about 4000 or less. In yet another embodiment, the molecular weight of the polyether amine is about 600 or greater. In still another embodiment, the molecular weight of the polyether amine is about 3000 or less. In yet another embodiment, the molecular weight of the polyether amine is between about 1000 and about 3000, and more preferably is between about 1500 to about 2500. Because lower molecular weight polyether amines may be prone to forming solid polyureas, a higher molecular weight oligomer, such as JEFFAMINE® D2000, is preferred.
  • a higher molecular weight oligomer such as JEFFAMINE® D2000
  • amines may be unsuitable for reaction with the isocyanate because of the rapid reaction between the two components.
  • shorter chain amines are fast reacting.
  • a hindered secondary diamine may be suitable for use in the prepolymer.
  • an amine with a high level of stearic hindrance e.g., a tertiary butyl group on the nitrogen atom, has a slower reaction rate than an amine with no hindrance or a low level of hindrance.
  • 4,4′-bis-(sec-butylamino)-dicyclohexylmethane (CLEARLINK® 1000) may be suitable for use in combination with an isocyanate to form the polyurea prepolymer.
  • Isocyanates for use with the present invention include aliphatic, cycloaliphatic, araliphatic, aromatic, any derivatives thereof, and combinations of these compounds having two or more isocyanate (NCO) groups per molecule.
  • the isocyanates may be organic polyisocyanate-terminated prepolymers.
  • the isocyanate-containing reactable component may also include any isocyanate-functional monomer, dimer, trimer, or multimeric adduct thereof, prepolymer, quasi-prepolymer, or mixtures thereof.
  • Isocyanate-functional compounds may include monoisocyanates or polyisocyanates that include any isocyanate functionality of two or more.
  • Suitable isocyanate-containing components include diisocyanates having the generic structure: O ⁇ C ⁇ N—R—N ⁇ C ⁇ O, where R is preferably a cyclic, aromatic, or linear or branched hydrocarbon moiety containing from about 1 to about 20 carbon atoms.
  • the diisocyanate may also contain one or more cyclic groups or one or more phenyl groups. When multiple cyclic or aromatic groups are present, linear and/or branched hydrocarbons containing from about 1 to about 10 carbon atoms can be present as spacers between the cyclic or aromatic groups.
  • the cyclic or aromatic group(s) may be substituted at the 2-, 3-, and/or 4-positions, or at the ortho-, meta-, and/or para-positions, respectively.
  • Substituted groups may include, but are not limited to, halogens, primary, secondary, or tertiary hydrocarbon groups, or a mixture thereof.
  • diisocyanates examples include, but are not limited to, substituted and isomeric mixtures including 2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanate; 3,3′-dimethyl-4,4′-biphenylene diisocyanate; toluene diisocyanate; polymeric MDI; carbodiimide-modified liquid 4,4′-diphenylmethane diisocyanate; para-phenylene diisocyanate; meta-phenylene diisocyanate; triphenyl methane-4,4′- and triphenyl methane-4,4′-triisocyanate; naphthylene-1,5-diisocyanate; 2,4′-, 4,4′-, and 2,2-biphenyl diisocyanate; polyphenyl polymethylene polyisocyanate; mixtures of MDI and PMDI; mixtures of PMDI and TDI; ethylene di
  • saturated diisocyanates examples include, but are not limited to, ethylene diisocyanate; propylene-1,2-diisocyanate; tetramethylene diisocyanate; tetramethylene-1,4-diisocyanate; 1,6-hexamethylene-diisocyanate; octamethylene diisocyanate; decamethylene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; dodecane-1,12-diisocyanate; cyclobutane-1,3-diisocyanate; cyclohexane-1,2-diisocyanate; cyclohexane-1,3-diisocyanate; cyclohexane-1,4-diisocyanate; methyl-cyclohexylene diisocyanate; 2,4-methylcyclohexane diisocyanate
  • Aromatic aliphatic isocyanates may also be used to form light stable materials.
  • isocyanates include 1,2-, 1,3-, and 1,4-xylene diisocyanate; meta-tetramethylxylene diisocyanate; para-tetramethylxylene diisocyanate; trimerized isocyanurate of any polyisocyanate, such as isocyanurate of toluene diisocyanate, trimer of diphenylmethane diisocyanate, trimer of tetramethylxylene diisocyanate, isocyanurate of hexamethylene diisocyanate, isocyanurate of isophorone diisocyanate, and mixtures thereof; dimerized uredione of any polyisocyanate, such as uretdione of toluene diisocyanate, uretdione of hexamethylene diisocyanate, and mixtures thereof; modified polyisocyanate derived from the above is
  • the number of unreacted NCO groups in the polyurea prepolymer of isocyanate and polyether amine may be varied to control such factors as the speed of the reaction, the resultant hardness of the composition, and the like.
  • the number of unreacted NCO groups in the polyurea prepolymer of isocyanate and polyether amine may be less than about 14 percent.
  • the polyurea prepolymer has from about 5 percent to about 11 percent unreacted NCO groups, and even more preferably has from about 6 to about 9.5 percent unreacted NCO groups.
  • the percentage of unreacted NCO groups is about 3 percent to about 9 percent.
  • the percentage of unreacted NCO groups in the polyurea prepolymer may be about 7.5 percent or less, and more preferably, about 7 percent or less.
  • the unreacted NCO content is from about 2.5 percent to about 7.5 percent, and more preferably from about 4 percent to about 6.5 percent.
  • polyurea prepolymers When formed, polyurea prepolymers may contain about 10 percent to about 20 percent by weight of the prepolymer of free isocyanate monomer. Thus, in one embodiment, the polyurea prepolymer may be stripped of the free isocyanate monomer. For example, after stripping, the prepolymer may contain about 1 percent or less free isocyanate monomer. In another embodiment, the prepolymer contains about 0.5 percent by weight or less of free isocyanate monomer.
  • the polyether amine may be blended with additional polyols to formulate copolymers that are reacted with excess isocyanate to form the polyurea prepolymer. In one embodiment, less than about 30 percent polyol by weight of the copolymer is blended with the saturated polyether amine. In another embodiment, less than about 20 percent polyol by weight of the copolymer, preferably less than about 15 percent by weight of the copolymer, is blended with the polyether amine.
  • polyether polyols e.g., polyether polyols, polycaprolactone polyols, polyester polyols, polycarbonate polyols, hydrocarbon polyols, other polyols, and mixtures thereof
  • polyether amine e.g., polyether polyols, polycaprolactone polyols, polyester polyols, polycarbonate polyols, hydrocarbon polyols, other polyols, and mixtures thereof
  • the molecular weight of these polymers may be from about 200 to about 4000, but also may be from about 1000 to about 3000, and more preferably are from about 1500 to about 2500.
  • the polyurea composition can be formed by crosslinking the polyurea prepolymer with a single curing agent or a blend of curing agents.
  • the curing agent of the invention is preferably an amine-terminated curing agent, more preferably a secondary diamine curing agent so that the composition contains only urea linkages.
  • the amine-terminated curing agent may have a molecular weight of about 64 or greater. In another embodiment, the molecular weight of the amine-curing agent is about 2000 or less.
  • certain amine-terminated curing agents may be modified with a compatible amine-terminated freezing point depressing agent or mixture of compatible freezing point depressing agents.
  • Suitable amine-terminated curing agents include, but are not limited to, ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine; 4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 1,4-bis-(sec-butylamino)-cyclohexane; 1,2-bis-(sec-butylamino)-cyclohexane; derivatives of 4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethane diamine; 1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine); diethylene glycol di-(aminopropyl)ether; 2-methylpentamethylene-di
  • Suitable saturated amine-terminated curing agents include, but are not limited to, ethylene diamine; hexamethylene diamine; 1-methyl-2,6-cyclohexyl diamine; tetrahydroxypropylene ethylene diamine; 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine; 4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 1,4-bis-(sec-butylamino)-cyclohexane; 1,2-bis-(sec-butylamino)-cyclohexane; derivatives of 4,4′-bis-(sec-butylamino)-dicyclohexylmethane; 4,4′-dicyclohexylmethane diamine; 4,4′-methylenebis-(2,6-diethylaminocyclohexane; 1,4-cyclohexane-bis-(methylamine); 1,3-cyclohexane-bis-(methylamine
  • Cover layers of the inventive golf ball may also be formed from ionomeric polymers, preferably highly-neutralized ionomers (HNP).
  • HNP highly-neutralized ionomers
  • at least one intermediate layer of the golf ball is formed from an HNP material or a blend of HNP materials.
  • the acid moieties of the HNP's typically ethylene-based ionomers, are preferably neutralized greater than about 70%, more preferably greater than about 90%, and most preferably at least about 100%.
  • the HNP's can be also be blended with a second polymer component, which, if containing an acid group, may be neutralized in a conventional manner, by the organic fatty acids of the present invention, or both.
  • the second polymer component which may be partially or fully neutralized, preferably comprises ionomeric copolymers and terpolymers, ionomer precursors, thermoplastics, polyamides, polycarbonates, polyesters, polyurethanes, polyureas, thermoplastic elastomers, polybutadiene rubber, balata, metallocene-catalyzed polymers (grafted and non-grafted), single-site polymers, high-crystalline acid polymers, cationic ionomers, and the like.
  • HNP polymers typically have a material hardness of between about 20 and about 80 Shore D, and a flexural modulus of between about 3,000 psi and about 200,000 psi.
  • the HNP's are ionomers and/or their acid precursors that are preferably neutralized, either filly or partially, with organic acid copolymers or the salts thereof.
  • the acid copolymers are preferably ⁇ -olefin, such as ethylene, C 3-8 ⁇ , ⁇ -ethylenically unsaturated carboxylic acid, such as acrylic and methacrylic acid, copolymers. They may optionally contain a softening monomer, such as alkyl acrylate and alkyl methacrylate, wherein the alkyl groups have from 1 to 8 carbon atoms.
  • the acid copolymers can be described as E/X/Y copolymers where E is ethylene, X is an ⁇ , ⁇ -ethylenically unsaturated carboxylic acid, and Y is a softening comonomer.
  • X is acrylic or methacrylic acid and Y is a C 1-8 alkyl acrylate or methacrylate ester.
  • X is preferably present in an amount from about 1 to about 35 weight percent of the polymer, more preferably from about 5 to about 30 weight percent of the polymer, and most preferably from about 10 to about 20 weight percent of the polymer.
  • Y is preferably present in an amount from about 0 to about 50 weight percent of the polymer, more preferably from about 5 to about 25 weight percent of the polymer, and most preferably from about 10 to about 20 weight percent of the polymer.
  • Specific acid-containing ethylene copolymers include, but are not limited to, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/n-butyl acrylate, ethylene/methacrylic acid/iso-butyl acrylate, ethylene/acrylic acid/iso-butyl acrylate, ethylene/methacrylic acid/n-butyl methacrylate, ethylene/acrylic acid/methyl methacrylate, ethylene/acrylic acid/methyl acrylate, ethylene/methacrylic acid/methyl acrylate, ethylene/methacrylic acid/methyl methacrylate, and ethylene/acrylic acid/n-butyl methacrylate.
  • Preferred acid-containing ethylene copolymers include, ethylene/methacrylic acid/n-butyl acrylate, ethylene/acrylic acid/n-butyl acrylate, ethylene/methacrylic acid/methyl acrylate, ethylene/acrylic acid/ethyl acrylate, ethylene/methacrylic acid/ethyl acrylate, and ethylene/acrylic acid/methyl acrylate copolymers.
  • the most preferred acid-containing ethylene copolymers are, ethylene/(meth)acrylic acid/n-butyl, acrylate, ethylene/(meth)acrylic acid/ethyl acrylate, and ethylene/(meth)acrylic acid/methyl acrylate copolymers.
  • Ionomers are typically neutralized with a metal cation, such as Li, Na, Mg, K, Ca, or Zn. It has been found that by adding sufficient organic acid or salt of organic acid, along with a suitable base, to the acid copolymer or ionomer, however, the ionomer can be neutralized, without losing processability, to a level much greater than for a metal cation.
  • the acid moieties are neutralized greater than about 80%, preferably from 90-100%, most preferably 100% without losing processability.
  • the organic acids of the present invention are aliphatic, mono- or multi-functional (saturated, unsaturated, or multi-unsaturated) organic acids. Salts of these organic acids may also be employed.
  • the salts of organic acids of the present invention include the salts of barium, lithium, sodium, zinc, bismuth, chromium, cobalt, copper, potassium, strontium, titanium, tungsten, magnesium, cesium, iron, nickel, silver, aluminum, tin, or calcium, salts of fatty acids, particularly stearic, behenic, erucic, oleic, linoelic or dimerized derivatives thereof. It is preferred that the organic acids and salts of the present invention be relatively non-migratory (they do not bloom to the surface of the polymer under ambient temperatures) and non-volatile (they do not volatilize at temperatures required for melt-blending).
  • the ionomers of the invention may also be more conventional ionomers, i.e., partially-neutralized with metal cations.
  • the acid moiety in the acid copolymer is neutralized about 1 to about 90%, preferably at least about 20 to about 75%, and more preferably at least about 40 to about 70%, to form an ionomer, by a cation such as lithium, sodium, potassium, magnesium, calcium, barium, lead, tin, zinc, aluminum, or a mixture thereof.
  • the inventive single-layer core is enclosed with two cover layers, where the inner cover layer has a thickness of about 0.01 inches to about 0.06 inches, more preferably about 0.015 inches to about 0.040 inches, and most preferably about 0.02 inches to about 0.035 inches, and the inner cover layer is formed from a partially- or fully-neutralized ionomer having a Shore D hardness of greater than about 55, more preferably greater than about 60, and most preferably greater than about 65.
  • the outer cover layer should have a thickness of about 0.015 inches to about 0.055 inches, more preferably about 0.02 inches to about 0.04 inches, and most preferably about 0.025 inches to about 0.035 inches, and has a hardness of about Shore D 60 or less, more preferably 55 or less, and most preferably about 52 or less.
  • the inner cover layer should be harder than the outer cover layer.
  • the outer cover layer comprises a partially- or fully-neutralized ionomer, a polyurethane, polyurea, or blend thereof.
  • a most preferred outer cover layer is a castable or reaction injection molded polyurethane, polyurea or copolymer or hybrid thereof having a Shore D hardness of about 40 to about 50.
  • a most preferred inner cover layer material is a partially-neutralized ionomer comprising a zinc, sodium or lithium neutralized ionomer such as SURLYN® 8940, 8945, 9910, 7930, 7940, or blend thereof having a Shore D hardness of about 63 to about 68.
  • the outer cover and inner cover layer materials and thickness are the same but, the hardness range is reversed, that is, the outer cover layer is harder than the inner cover layer.
  • the golf ball is a one-piece golf ball having a dimpled surface and having a surface hardness equal to or less than the center hardness (i.e., a negative hardness gradient).
  • the one-piece ball preferably has a diameter of about 1.680 inches to about 1.690 inches, a weight of about 1.620 oz, an Atti compression of from about 40 to 120, and a COR of about 0.750-0.825.
  • the single-layer core having a negative hardness gradient is enclosed with a single layer of cover material having a Shore D hardness of from about 20 to about 80, more preferably about 40 to about 75 and most preferably about 45 to about 70, and comprises a thermoplastic or thermosetting polyurethane, polyurea, polyamide, polyester, polyester elastomer, polyether-amide or polyester-amide, partially or fully neutralized ionomer, polyolefin such as polyethylene, polypropylene, polyethylene copolymers such as ethylene-butyl acrylate or ethylene-methyl acrylate, poly(ethylene methacrylic acid) co-and terpolymers, metallocene-catalyzed polyolefins and polar-group functionalized polyolefins and blends thereof.
  • a thermoplastic or thermosetting polyurethane such as polyethylene, polypropylene, polyethylene copolymers such as ethylene-butyl acrylate or ethylene-methyl acrylate, poly(ethylene methacrylic
  • a preferred cover material in the two-piece embodiment is an ionomer (either conventional or HNP) having a hardness of about 50 to about 70 Shore D.
  • Another preferred cover material in the two-piece embodiment is a thermoplastic or thermosetting polyurethane or polyurea.
  • a preferred ionomer is a high acid ionomer comprising a copolymer of ethylene and methacrylic or acrylic acid and having an acid content of at least 16 to about 25 weight percent.
  • the reduced spin contributed by the relatively rigid high acid ionomer may be offset to some extent by the spin-increasing negative gradient core.
  • the core may have a diameter of about 1.0 inch to about 1.64 inches, preferably about 1.30 inches to about 1.620, and more preferably about 1.40 inches to about 1.60 inches.
  • Another preferred cover material comprises a castable or reaction injection moldable polyurethane, polyurea, or copolymer or hybrid of polyurethane/polyurea.
  • this cover is thermosetting but may be a thermoplastic, having a Shore D hardness of about 20 to about 70, more preferably about 30 to about 65 and most preferably about 35 to about 60.
  • a moisture vapor barrier layer such as disclosed in U.S. Pat. Nos. 6,632,147; 6,932,720; 7,004,854; and 7,182,702, all of which are incorporated by reference herein in their entirety, are optionally employed between the cover layer and the core.
  • a preferred number of dimples is 252 to 456, and more preferably is 330 to 392.
  • the dimples may comprise any width, depth, and edge angle disclosed in the prior art and the patterns may comprises multitudes of dimples having different widths, depths and edge angles.
  • the parting line configuration of said pattern may be either a straight line or a staggered wave parting line (SWPL). Most preferably the dimple number is 330, 332, or 392 and comprises 5 to 7 dimples sizes and the parting line is a SWPL.
  • the single-layer core may be replaced with a 2 or more layer core wherein at least one core layer has a negative hardness gradient.

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US11/829,461 US7537530B2 (en) 2007-07-03 2007-07-27 Golf ball with negative hardness gradient core
US11/832,197 US7410429B1 (en) 2007-07-03 2007-08-01 Negative hardness gradient inner core for dual core golf ball
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US7857715B2 (en) * 2007-07-03 2010-12-28 Acushnet Company Negative hardness gradient inner core for dual core golf ball
US9636549B2 (en) * 2007-07-03 2017-05-02 Acushnet Company Negative hardness gradient inner core for dual core golf ball
US20100004071A1 (en) * 2007-07-03 2010-01-07 Bulpett David A Negative hardness gradient inner core for dual core golf ball
US9149689B2 (en) 2007-11-14 2015-10-06 Acushnet Company Dual core golf ball having positive-hardness-gradient thermoplastic inner core and positive-hardness-gradient thermoset outer core layer
US8727912B2 (en) 2007-11-14 2014-05-20 Acushnet Company Dual core golf ball having negative-hardness-gradient thermoplastic inner core and shallow positive-hardness-gradient thermoset outer core layer
US8182369B2 (en) 2007-11-14 2012-05-22 Acushnet Company Dual core golf ball having negative-hardness-gradient thermoplastic inner core and shallow positive-hardness-gradient thermoset outer core layer
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US20110237351A1 (en) * 2007-11-14 2011-09-29 Sullivan Michael J Dual core golf ball having negative-hardness-gradient thermoplastic inner core and shallow positive-hardness-gradient thermoset outer core layer
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US8734273B2 (en) * 2010-12-22 2014-05-27 Sri Sports Limited Golf ball
US20120165123A1 (en) * 2010-12-22 2012-06-28 Tachibana Kosuke Golf ball
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CN104338294B (zh) * 2013-08-05 2017-04-12 阿库施耐特公司 多层芯高尔夫球

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US20100004071A1 (en) 2010-01-07
US20150224368A1 (en) 2015-08-13
US20100004073A1 (en) 2010-01-07
US7857714B2 (en) 2010-12-28
US9636549B2 (en) 2017-05-02
US20100004070A1 (en) 2010-01-07
US7410429B1 (en) 2008-08-12
US20090011859A1 (en) 2009-01-08
US7803069B2 (en) 2010-09-28
US9011271B2 (en) 2015-04-21
US20090011863A1 (en) 2009-01-08
US7857715B2 (en) 2010-12-28

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